Light projector fop strcboscopic and otheh purposes



Feb. 28, 1939. A. J. ASHDOWN LIGHT PROJECTOR POP STROBOSCOPIC AND OTHERPURPOSES Filed July 1:5, 19% 3 Sheets-Sheet 1 Feb. 28, 1939. A. J.ASHDOWN 2,148,794

LIGHT FROJECTOR FOR STROBOSCOPIC AND OTHER PURPOSES Filed July 13, 19363 Sheets-Sheet 2 PEP W 3 Sheets-Sheet 3 INVENTOP mean/mm m.\ 0 E\\\\ \N7 0%- 0Q! A. J. ASHDOWN LIGHT PROJECTOR FOR STROBOSCOFIC AND OTHERPURPOSES Filed July 15, 1936 can.

L amen a \v $6 $6 RM H .1 00m.

NM QBN own- 009 PatentedFeb. 28, 1939 chm) STATES LIGHT PROJECTOR Fons'rnonosoorro AND OTHER PURPOSES Albert Jasper Ashdown, East Molesey,England Application July 13, 1936, squirm-90,407

In Great Britain July 17, 1935 1. Claim.

This invention comprises improvements in and relating to lightprojectors for stroboscopic and other purposes. The chief object of thisinvention is to provide a light projectorior stroboscopic purposes inwhich an intermittent beam of concentrated light is projected directlyby a light converging reflectorrirom a casing enclosing the light sourceand reflector, and in such direction relative to the casingas to ensurea great con-' venience of handling or setting of the casing and easyaccess to various parts of machinery to be inspected, andalso a veryintense beam of concentrated light rayson the desired object. An-

other object of the invention is to provide a simple, compact andreadily portable apparatus which can be held conveniently in one handand operated by the hand holding it for projecting a strong beam oflight intermittently or periodically upon an object and also to providemeans wherebygo the beam of light may be concentrated so as to give anintense illumination over a clearly defined area ior a comparativelyshort space 01' time and at regularly spaced intervals. The apparatuscan be used to enable moving'objects to be viewed for short periods at.regularly spaced intervals which may be'faccurately'timed to any desiredperiodicity. The apparatus may be so timed that the beam of light isprojected upon the ob-, ject for a comparatively short period whilst theintervening space of time during which the beam of light doesnotilluminate the object is of relatively much longer duration. j 1 Thelight projector may be employed ior direct vision stroboscopicpurposes-in which the object is viewed directly by the observer withoutthe use of any other apparatus than the light projector which, causesthe object to be illuminated ior relatively short periods spaced atdeflnit time intervals apart. The apparatus may also be employed 49 inconnection with speed testing and checking and enables the speed oimoving objects such as shafts,

pulleys andthe like to' be observed, ascertaifiedor checked without thenecessity for the observer or anyone'elseappmaching close to orgigtually touching the shaft or other moving ob- It isprererred toconstruct my light projector in. the form of a simple portable unitadapted to be carried in the hand so that the-beam of light so maybedirected so that it will tall intermittently upon an'object to beobserved, or where pmlonged observation is required it may be mounteduponastandinsuchanadjustablemannerasto enable the beam- 01 light to beprojected in the irequireddirectiou. a V

made in accordance with the present invention.

Fig. 2 is an end view partly in section of same projector; and Fig. 3 isa view similar to Fig. 1 but showing a modified form of the lightprojector.

Referring flrstto Fig. 1, a casing I has a-pi stol grip handle 5 wherebyit can be conveniently held in one hand and pointed at the desired zone,and a lid 8 which can be opened or removed. Mounted within the casing isan electric motor I having a rapidly rotatable spindle 8 carrying aholder 9 for the reflecting device i0 which is aconcave mirror. Themirror is adjustable and is arranged at a suitable angle to the axis ofthe spindle 8.

the

The mirror faces an opening i2 in thecasing and adjacent to this openingis a tubular member or casing l3 attached to the main casing l at oneend and extending outwardly from the main casing. The tubular casing l3has a longitudinal slot opening it between its ends and in its outer endis removably fitted a small holder or casing I! which carries the lightsource it comprising an electric light bulb, and a reflector II. Byproviding an opening such as I4 and locating a lens mirror 10 close tothe inner end of such slot like openingjthe light beam from the sourceit is collected by the rotating lens reflector and reflected back in acone of light the axis of which is' always at only a small angle to theaxis of the light beamsirom the light source. By this means the area oflight. The reflector I1 is of parabolic or 45 other form adapted tocollect and concentrate the light beam upon. the .iil'lOl. A lens I8 isfitted in the small casing and the latter can be adjusted towards oraway from the concave mirror by pin and slot II. Electric. current issupplied to the electric bulb through a flex II which may be connectedto the'malns or a dry cell battery 22 mounted on the lid of themalncasing. The current for the electric motor may also be taken "fromthe'xnains or from this dry cell battery.

'Suitable connectionsmay be provided on the electric motor to the sourceof current and a suitable switch or switches may be incorporated forcontrolling the supply of current to the lamp or the electric motor orboth. The beam of light from the bulb l6 and reflector l'i. will bedirected on to the mirror Ill at such a spot thereon that the reflectedbeam from the mirror will generate a frustoconical figure and willperiodically project through the opening !4. This results from themovement of the mirror which is similar to that of a swash-plate.

The apparatus may be held so as to direct the moving beam of light sothat it will fall intermittently upon the object to be viewed. Inworkshops or other closed premises where a highly concentrated lightdoes not fall upon the object to' be viewed, the device may be used inordinary daylight since the concentrated beam of light projectedintermittently on to the object may be of a far greater intensity thanthe surrounding illumination so that the periods of illumination by theprojector will stand out definitely and give intermittent glimpses ofthe object of short duration spaced at relatively long intervals apartand thus enabling a stroboscopic view of the object to be obtained. Theinvention may also be usedfor speed testing of shafts or other movingobjects by observing the spokes of pulleys or other definitely spacedobjects arranged upon the shaft or a, moving member on it.

The concave mirror is of a suitable focal length and the source of lightis arranged at such a arranged in relation to the light source that the,

light falling upon the object shall be concentrated within a clearlydefined area and so far as possible without any penumbra or surroundingzone of lesser illumination.

For maintaining the speed of the motor constant a toothed wheel 28 isfixed to the rear end of the motor spindle 8 and cooperating with thistoothed wheel is a detent 2! carried by a vibratory member comprising atuning fork 28 as described in the specification of my British PatentNo. 363,352. Other suitable control means may however be provided.

The arrangement shown in Fig. 3 resemble that shown in Figs. 1 and 2 inmany respects and similar reference numerals are applied whereappropriate. I

The small casing I5 is readily removable from the tubular casing l3 forcleaning or adjustment and is provided with an optical condensingsystem. Instead of a plain glass 18 a'lens we can.

be employed to effect the desired projection of light on to the mirrorill.

The main casing 4 contains a change speed gear and governor controlledbrake made on the lines indicated in my prior British Patent No.201,656. The motor spindle B is geared by gear amazes wheels 30, 3i,with a stub shaft 32.

shaft that carries the governor 36 having a brake disc 31. 'Ihe usualbrake block 31a engaging this disc can be moved towards or away from thedisc by rotating a speed indicator wheel do which has numeralsindicative of speed on its periphery. The wheel 40 can carry a worm 40bmeshing with a worm wheel 40a the spindle of which has a crankconnection 11a to a link 11 connected to a brake lever 31b carrying thebrake pad 31a. The stub shaft 32 is connected bygear wheels 32, 53, witha layshaft 44 that carries a slidable splined sleeve 45. The sleeve 45carries pinions 47, 38, 49, 50, 5|, adaptedto be brought into gear withpinions 52, 53, 54, 55, 56, respectively, by slidable movement ofthe'sleeve 45, for eiiecting change of speed of rotation of the concavemirror Ill. The pinions 52--56 are fixed to a spindle which is connectedby pinions 56, 62, with "a stub shaft: 63 which in turn drives a spindle6 8 through pinions 65, 66. The'spi'ndle 64 is mounted in a bearing 61attached m the casing d and the mirror I0 is mounted on the spindle 56its angle being adjustable by the screw device 10. The sliding of thesleeve 45 can be accomplished by a striking gear comprising a lever 12which is pivotally mounted at its upper end on a fixed part and engagesat its lower end between collars 12a on the sleeve. The lower end has alink M attached to it the lower end of which link can be moved by theoperator and fixed many of the appropriate notches in a gate- 16.

ing from said housing, an electric motor in the housing, a triggerswitch adjacent to said handle for bringing the motor into and out ofcircuit, an opening in one end of the housing, .a tubular easingextending beyond said opening, a reflector and lamp at the free end ofthe tubularcasing having an optical axis substantially coincident withthe axis of the tubular 'casing, a rotary member driven by said motorand located close to and opposite said opening; a longitudinal slot insaid casing, and a converging reflector on said rotary member inclinedin relation to said axis so as to collect and reflect light .from saidlamp, said reflector having'an axis of reflection of the light from saidlamp which is at such an angle to'said optical axis so as to direct'abeam of light along said casing so that it-passes through said The wheelcasing for connecting the-electric lamp and the 3i also gears with apinion 34 on the governor ill) slot intermittently at a small angletothe axis of said casing. ALBERT JASPER ASHDOWN.

